Diary: sandbox 90% done, piclaudeio idea

DIARY.md

@@ -498,3 +498,22 @@ follows the Microsoft HID-over-I2C v1.0 spec. The real risk is:
 1. Keyboard power regulator not enabled (GPIO1_A7)
 2. Interrupt GPIO not configured correctly
 3. pct13x2 might have non-standard HID quirks
+
+## Day 2 3AM: Sandbox Keyboard Progress
+
+Got the U-Boot sandbox running with:
+- HID-over-I2C keyboard driver (patch 0006) compiled in
+- I2C HID emulator (custom sandbox driver) bound
+- i2c@5 bus appearing in `i2c bus` output (Bus 1)
+- Emulator visible in `dm tree` as `hid_i2c_emul emul-hid-kbd`
+
+The KEY insight from the research agent: sandbox uses `test.dts` (via -T flag),
+NOT `sandbox.dts`. We spent an hour modifying the wrong file.
+
+Remaining issue: the emulator `xfer` function isnt being called during
+`i2c probe` or `i2c md`. The emulator is bound but not probed (lazy binding).
+The sandbox I2C bus auto-probe mechanism isnt matching our device to its
+emulator. Likely a small detail in the phandle dispatch or ops registration.
+
+Also discussed: piclaudeio protocol using ASCII record/field separators
+(0x1E/0x1F) for escaping, netstrings for binary. Would solve the heredoc hell.